This invention relates to heat exchangers and more particularly to heat exchangers having double wall tubes and three tube sheets.
It is desirable to ensure the separation of heating and heated fluids in heat exchangers and depending on the compatibility of the fluids involved, the effort and expense expended to ensure the separation of these fluids varies. Double wall tubes with grooves in one of the walls at the interface have been proposed as a highly reliable method of maintaining the separation between the fluids. However, two tube sheet junctures are susceptible to leaks. Double tube sheets on each end of the tubes may be utilized to detect leaks at the tube-to-tube sheet juncture further decreasing the possibility of undetected leaks and admixing of the two fluids.